1. Field of the Invention
The present invention relates to a conical filter and in particular to a conical filter of fluted filter media for placement inline in a fluid stream, and a method for making the filter.
2. Description of the Prior Art
Fluid filters are used for a wide variety of applications. Fluid filters typically use a filter element inside of a housing having an inlet and an outlet so that the fluid passes through the filter media, thereby trapping particulate material. Aerodynamic conical filters are generally used for high velocity fluid flow applications, such as automobile air intake filters. In the past there has been little usage of conical filters mainly due to problems with size and effectiveness. Generally, these filters have used pleated filter media. With the pleated filters, straight through flow is not possible. This causes high pressure differentials across the filter and flow distribution problems. To combat these problems, designers have generally increased the spacing between the pleats, thereby reducing the density of the filter media. This has reduced the effective life of the filters and has not solved the flow distribution problem. These filters have also had the added problem in that the filter media is not self supporting. Generally, rigid housings are required for use of these filters.
Another shortcoming with typical prior filter designs is unequal flow distribution. Flow is often directed to a center portion of filters, thereby loading the filter unevenly. Portions of the filter may load over a much shorter interval, thereby requiring replacement of the filter element. However, if flow were directed more evenly over the entire filter, loading would be more uniform and more gradual, so that the filter life is extended.
An example of a conical filter is shown in U.S. Pat. No. 5,106,397, issued to Ford Motor Company, Apr. 21, 1992. In this patent, a pleated filter is used to filter air to an engine. To force air through the media, the top of each pleat is sealed together so that air cannot escape through gaps in the media. This allows an opening between each pleat for air to enter and flow down the pleat, through the media and out the inside center of the filter. In order to avoid restricting the incoming air, the pleats must be spaced, thus limiting the amount of filtering media available for filtering. An increase in filtering media results in an increase in pressure differential across the filter. Furthermore, for the air to enter the filtering media, it must make a sharp directional turn so as to pass through the filter media, thereby increasing the pressure drop across the filter.
It can be seen then, that an improved conical filter is needed which provides for increased filtering area without an accompanying high pressure differential across the filter. Such a filter should also provide for improved flow distribution and even loading over the entire filter. The present invention addresses these as well as other problems associated with conical filters.